Electrical transformers have been widely used in welding power supplies to transfer electrical energy between a source and a load circuit by employing a magnetic field which links the source and the load circuits. Electrical transformers have been used for changing voltage, matching impedencies and isolating circuits.
For many of these applications, an inductance was required to ensure proper performance of the power supply. Accordingly, it was necessary to add a separate inductor to the circuit. The separate inductor added circuitry, weight, cost and complexity to the device. Specifically, in the portable welder environment, the addition of circuitry, complexity, costs and weight has a substantial impact.
The prior art has combined the transformer and inductor in a single unit in an attempt to address the above-noted concerns. Typically, a combined transformer and inductor core element was provided with two flux line paths, one path for the inductors DC flux and one path for the transformers AC flux. The inductor flux line path is comprised of a core path that has an air gap around which the inductive winding are wound. The transformer primary and secondary windings were wound about a continuous core element having no air gap.
These improvements enhanced the art of transformer construction for circuits requiring an inductance. An advantage of combining the transformer and inductor was to eliminate the need for two separate mountings and for combining the transformer windings and the inductance windings around a single transformer and inductor core frame. This resulted in a reduction in weight and material cost in the combined units.
These prior art combined transformer and inductor apparatus have been widely and used for low power applications. These prior art combined transformers have been used significantly in the portable welder environment because reduction in weight and material costs are substantial features in the portable welder market. Industry developments have caused a need for portable welders that are adaptable to standard 60 Hz 120 VRMS volt inputs to be capable of high current outputs, while maintaining low current input requirements in accordance with UL and CSA requirements. However, the combined transformer and inductor apparatus disclosed in the prior art are not well suited for high power applications that allow for power inputs within the UL and CSA requirements. Complications arise when the prior art combined transformer and inductor apparatus were operated at high power levels. The power limitations are related to heat dissipation and that higher power output requires higher power inputs.
With the advent of demand for higher power output levels for portable welders that function within the power input requirements set forth by UL and CSA standards, there arose a need for a single core combined transformer and inductor apparatus capable of operating at high power levels, while still operating within the UL and CSA input power requirements. Merely increasing the scale of the prior art designs by making cores and coils larger is not a viable solution in the portable welder environment. In addition, the prior art combined transformers and inductors had substantial problems resulting from the previous single core combined transformer and inductor apparatus because there was a level of flux leakage from the inductor portion of the core into the limbs of the transformer core. Leakage of inductor DC flux into a transformer center limb causes a reduction in transformer efficiency, resulting in excessively high heat generation. The reduction in efficiency requires an increase in power input in order to achieve higher power output. In the prior art single core combined transformer and inductor apparatus the increase in input current was above the threshold level requirements set by UL and CSA. Accordingly, the prior art designs of single core combined transformer and inductor apparatuses have been satisfactory for low power applications but have not been satisfactory for high power applications wherein the input requirements are within UL and CSA standards. As a result, welder power supply circuitry that has high power output requirements and input power requirements that are within the CSA and UL requirements, such as the circuitry disclosed in U.S. Pat. No. 5,426,409, utilized separate transformer and inductor cores in order to comply with UL and CSA standards. There is a need for a single core combined transformer and inductor apparatus that allows a welder power supply to achieve higher power output levels while at the same time satisfying the UL and CSA requirements and reducing some of the problems associated with prior art combined transformer and inductors.
Therefore, it is an object of the present invention to provide an improved single core combined transformer and inductor apparatus for use in welder power supplies that reduces problems caused by higher power output requirements while satisfying UL and CSA requirements.
It is an object of the invention to reduce the weight, material costs and complexity within the power supply of a portable arc welder.